There is disclosed in DE-U-81 36 066 an endoscope for endonasal surgery, which has a suction and flushing shaft accommodating an optical system and a handle for releasable connection to said shaft. A valve is accommodated in the handle, by means of which valve the suction channel can be shut off by operating the valve and the flushing channel opened for infeeding a flushing fluid. The construction of the valve is such that the suction, or vacuum channel cannot be cleansed during use of the endoscope, which may for example be necessary if such channel is partly or wholly blocked by bodily secretions, pieces of tissue or the like, whereby use of the endoscope is at least restricted or is even wholly prevented. In such case the endoscopic examination must be suspended and the clogged shaft replaced by another shaft. Since the cleansing of such shafts is not usually carried out at the site of use, that is to say not immediately but at a later time, the suction channel must not only be subjected to normal disinfection or sterilisation but must also be mechanically cleaned in order to remove hardened or encrusted material thereform. Also, the handle is so shaped that it needs to be fully enclosed by the hand in order to use the endoscope.